X87: [turbofan] Implemented the optional Float32RoundDown operator.

  port 74434403 (r32261)

  original commit message:
  I implemented the optional Float32RoundDown operator on x64, ia32, arm,
  and arm64.

  For arm I also had to adjust the simulator.

BUG=

Review URL: https://codereview.chromium.org/1490113003

Cr-Commit-Position: refs/heads/master@{#32492}

src/compiler/x87/code-generator-x87.cc

@@ -834,6 +834,23 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       __ lea(esp, Operand(esp, kFloatSize));
       break;
     }
+    case kX87Float32Round: {
+      RoundingMode mode =
+          static_cast<RoundingMode>(MiscField::decode(instr->opcode()));
+      // Set the correct round mode in x87 control register
+      __ X87SetRC((mode << 10));
+
+      if (!instr->InputAt(0)->IsDoubleRegister()) {
+        InstructionOperand* input = instr->InputAt(0);
+        USE(input);
+        DCHECK(input->IsDoubleStackSlot());
+        __ fstp(0);
+        __ fld_s(i.InputOperand(0));
+      }
+      __ frndint();
+      __ X87SetRC(0x0000);
+      break;
+    }
     case kX87Float64Add: {
       __ X87SetFPUCW(0x027F);
       __ fstp(0);

src/compiler/x87/instruction-codes-x87.h

@@ -43,6 +43,7 @@ namespace compiler {
   V(X87Float32Min)                 \
   V(X87Float32Abs)                 \
   V(X87Float32Sqrt)                \
+  V(X87Float32Round)               \
   V(X87LoadFloat64Constant)        \
   V(X87Float64Add)                 \
   V(X87Float64Sub)                 \

src/compiler/x87/instruction-selector-x87.cc

@@ -842,7 +842,11 @@ void InstructionSelector::VisitFloat64Sqrt(Node* node) {
 }
 
 
-void InstructionSelector::VisitFloat32RoundDown(Node* node) { UNIMPLEMENTED(); }
+void InstructionSelector::VisitFloat32RoundDown(Node* node) {
+  X87OperandGenerator g(this);
+  Emit(kX87Float32Round | MiscField::encode(kRoundDown),
+       g.UseFixed(node, stX_0), g.Use(node->InputAt(0)));
+}
 
 
 void InstructionSelector::VisitFloat64RoundDown(Node* node) {
@@ -1310,7 +1314,8 @@ InstructionSelector::SupportedMachineOperatorFlags() {
   flags |= MachineOperatorBuilder::kFloat64RoundDown |
            MachineOperatorBuilder::kFloat64RoundUp |
            MachineOperatorBuilder::kFloat64RoundTruncate |
-           MachineOperatorBuilder::kFloat64RoundTiesEven;
+           MachineOperatorBuilder::kFloat64RoundTiesEven |
+           MachineOperatorBuilder::kFloat32RoundDown;
   return flags;
 }